A better drug than Tamoxifen for breast cancer?
In a press release by Reuters, their health correspondent advises us that there is now a much better drug to combat breast cancer than tamoxifen. The press release states that "Women with breast cancer who took Arimidex, made by AstraZeneca, were less likely to have their breast cancer come back and less likely to have it spread". This is great news for women with breast cancer, but how accurate is it?
The study that provides this information is published in The Lancet, v 364, December 4, 2004, on-line. If we read the study, we see that within the Margins of Error some of these statements are questionable:
After a follow-up of almost seven years, Arimidex significantly prolonged disease-free survival. The Risk Ratio was 0.87 (Margin of Error 0.78 to 0.97). That means that Arimidex takers had a lower risk (87%) compared to tamoxifen takers.
The Risk Ratio for metastizing (in distant sites) was 0.86 (Margin of Error 0.74-0.99) compared to tamoxifen takers.
The Risk ratio for the tumor spreading to the other breast was 0.58 (Margin of Error 0.38 to 0.88).
The problem with this study is its large Margin of Error, that raises the possibility (at least for the first two results) that Arimidex is no better than tamoxifen (Risk Ratio within the Margin of Error comes close to 1.0). However, it is also possible that Arimidex is even better than stated, if the lower value of the margin of error ultimately turns out to be the better estimate.
We conclude that women are certainly no worse off taking Arimidex, and possibly they may have a better prognosis, although the much higher price of Arimidex may not be justified completely by this study.